Digital LC Meter Version ll
An "improved" inductance/capacitance meter by Phil Rice, VK3BHR & Bob Innes, ZS6RZ.
[Close on 90 of these kits have been sold to date – all are working, without any problems!]
Inductance: 0.15uH to 200mH
Capacitance: 0.1pF to 1uF (non-electrolytic!)
Self-calibrating: Upon switch-on
Display: In pF, nF or uH, mH
Power: Any voltage between 9 and 12 Volts D.C. (Unit has a built-in regulator)
This unit has been compared with an HP Inductance meter, and found to be extremely accurate, in spite of being so simple.
It differs from the original in that:
A 16F628A PIC is used instead of the old discontinued PIC16F84A. The PIC16F628A has an internal comparator, which means the LM311 is no longer needed.
Software calibration is used. The finished meter can be calibrated against "any" accurate capacitor within the range 100pF to about 10000pF.
A capacitor is supplied to calibrate your meter. (Reddish/orange in colour) Capacitance is marked.
The relay is driven by an NPN transistor, to protect the PIC, which only sinks 30mA at most.
The inductance measuring function is automatically calibrated after calibrating the capacitance function. When testing inductances, “zero” the meter – by shorting the terminals/leads together.
To measure inductance, short the two measuring leads together, and press “zero” This will zero the inductance range of the meter. The inductance and capacitance of the leads will be zero’d out as well.
In both cases, the amount of stray capacitance and inductance is not worth crying about, as it is minimal, providing the test lead connections from the PC board are nice and thick.
See my website for more info and pricing!
Bob Innes............ZS6RZ BiCraft Electronics
Mobile Phone: 083 625 0294 (Business hours only)